Multi-beamforming method of four-dimensional antenna array based on space-time joint baseband modulation

Abstract

The present invention discloses a space-time joint baseband modulation four-dimensional antenna array multi-beam forming system, which includes a modulation timing generator, a baseband signal processor, a mixer, a power splitter / combiner, a time modulation switch, a filter, an amplifier, a circulator, an antenna unit, and optical fibers and cables connecting the various parts; the system uses digital baseband modulation and analog time modulation degrees of freedom to map multi-path signals to each antenna unit as needed, thereby realizing simultaneous same-frequency multi-beams. The present invention also discloses a space-time joint baseband modulation four-dimensional antenna array multi-beam forming method, which can realize multi-beam scanning without a phase shifter by changing the baseband pre-modulation signal; by optimizing the timing, the amplitude weighting value can be changed, and each beam is amplitude weighted, so as to realize the generation and shaping of simultaneous multi-beams at a lower hardware complexity.

Description

Technical Field

[0001] The present invention belongs to the field of antenna engineering technology and relates to the field of array signal processing. Specifically, based on four-dimensional antenna array technology and taking into account the digital baseband modulation degrees of freedom and analog time modulation degrees of freedom, a low-complexity, highly flexible multi-beam forming system and method are proposed. The system and method can be used in wireless electronic systems requiring flexible multi-beams. Background Art

[0002] In 1963, American scholars Kummer et al. proposed the concept of a time-modulated antenna array: by continuously changing the antenna state over time, the antenna's radiation aperture size can be controlled in the "time" dimension. A time-modulated antenna array is a type of four-dimensional antenna array. Four-dimensional antenna arrays use high-speed RF modulation switches, high-speed amplitude and phase modulators, mixers, and other devices to control the operating state of each element according to a predetermined operating sequence, allowing the array's radiation state to vary over time. This characteristic, known as time modulation, increases the design freedom of the array antenna and overcomes the performance bottlenecks of traditional array antennas. Four-dimensional antenna arrays demonstrate significant advantages in high-precision beamforming and have achieved numerous results. In recent years, research on the engineering applications of four-dimensional antenna arrays has received increasing attention. Literature has reported on the application of four-dimensional antenna arrays in simultaneous multi-beam scanning, secure communications, and low-probability-of-intercept radar. As a new type of array antenna with extremely flexible design, the beamforming capability of four-dimensional antennas is expected to break through the beamforming bottlenecks of traditional arrays and enable flexible multi-beam scanning.

[0003] Currently, due to the high cost and energy consumption of digital channels, digital beamforming (DBF) technology, while offering extremely high beam steering flexibility, is difficult to implement in large-scale antenna arrays. On the other hand, while traditional phased array analog beamforming technology offers the advantages of low cost, low energy consumption, and suitability for large arrays, its beam steering flexibility is often far inferior to that of digital beamforming. Therefore, to address the issue of flexible multi-beamforming for large-scale arrays, numerous scholars in related fields have proposed numerous novel analog multi-beam generation methods.

[0004] Patent publication number CN 116318278 B proposes a multi-beamforming network and a six-beam base station antenna. This antenna utilizes multiple interconnected analog networks capable of amplitude weighting and resonant phase modulation to generate simulated multi-beams. However, the complex structure of this analog network limits the control freedom of the resulting multi-beams, making it difficult to independently control each beam.

[0005] Patent publication number CN 115589241 B proposes a four-dimensional antenna multi-beamforming method and system based on phase modulation. This method uses phase modulation to simultaneously transmit beams of multiple harmonic frequencies. At the receiving end, the corresponding harmonic beams are obtained by filtering the received signals through a filter. However, the multiple beams transmitted by this method and system are not only at different frequencies, but also rely solely on the phase modulation degree of freedom to control the beams, resulting in limited beam flexibility and difficulty in flexibly adjusting the multi-beam pointing direction.

[0006] Patent publication number CN 117713942 A proposes a device and method for simultaneously transmitting multiple beams from a phased array. This method utilizes wavelength division multiplexing (WDM) to transmit multiple signals to each antenna element, achieving high-precision simultaneous multi-beam scanning. However, this device and method require complex optoelectronic and electro-optical conversion, resulting in extremely complex hardware and limited support for large-scale array applications.

[0007] In the paper "A General Approach for Synthesizing Multibeam Antenna Arrays Employing Generalized Joined Coupler Matrix," Charles A. Guo et al. proposed the concept of a generalized joined coupler matrix. By cascading couplers and adding corresponding phase shifter networks, multiple simulated beams can be generated, and the phase shifters can be adjusted to control the direction of each individual beam. However, cascading couplers and phase shifters is not only complex but also leads to cascaded errors, resulting in low beam control accuracy.

[0008] To address these application needs, the present invention discloses a system and method for multi-beamforming in a four-dimensional antenna array using space-time joint baseband modulation. By combining the degrees of freedom of digital baseband modulation with the degrees of freedom of analog time modulation, multi-path signals are mapped as needed to each antenna element, thereby achieving simultaneous, co-frequency multi-beaming. The pointing direction of each beam can be arbitrarily adjusted while suppressing its sidelobe level. This method fully utilizes the space-time degrees of freedom of the four-dimensional antenna array, generating simultaneous, co-frequency multi-beaming with flexible control of beam pointing and sidelobe level, while maintaining low hardware complexity. Summary of the Invention

[0009] The present invention is realized in view of the above background, overcomes the shortcomings of the existing technology, and proposes a space-time joint baseband modulation four-dimensional antenna array multi-beam forming system and method, which realizes simultaneous and same-frequency multi-beam generation with low hardware complexity.

[0010] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions. Consider a four-dimensional antenna array with N units, whose time domain radiation field can be expressed as

[0011]

[0012] Where f0 is the carrier frequency, N is the number of antenna units, and U k (t) represents the timing function of the kth unit, β represents the wave number in free space (β can usually be set to 2π / λ, where λ represents the wavelength of free space), d represents the distance between two adjacent units, θ represents the angular direction, t represents time, e represents the natural base, and j represents the imaginary unit.

[0013] When U k When (t) is considered as a periodic function, the radiation field of the four-dimensional antenna array can be expanded in the frequency domain as follows:

[0014]

[0015] in,

[0016]

[0017] Where a mk represents the equivalent complex excitation of the kth unit at the mth-order sideband, including amplitude and phase terms, f p Indicates the modulation frequency of the timing signal, T p Indicates the modulation period of the timing signal, t k Indicates the conduction start time, τ k Indicates the on-time duration.

[0018] Due to the nonlinear time-varying effect of the time modulation of the four-dimensional antenna array, the transmit beam and receive beam characteristics of the four-dimensional antenna array are difficult to understand directly through the reciprocity principle. Therefore, it is necessary to describe the transmit and receive beamforming methods of the four-dimensional antenna array separately in combination with the specific signal flow direction.

[0019] First, consider the case where a four-dimensional antenna array is used for transmission. Assuming that multiple beams are used to transmit multiple signals, the total baseband signal is obtained by multi-path signals through baseband premodulation signal h. p (t) is modulated and summed to produce:

[0020]

[0021] where s p (t) is the wave that needs to be transmitted from the pth beam to θ p The pth signal in the direction, Q represents the number of signal paths to be transmitted, h p (t) is the s transmitted by the pth beam p The corresponding baseband premodulation signal (t) can be expressed as:

[0022]

[0023] In this way, the radiation field of the four-dimensional antenna array carrying the baseband signal s(t) can be expressed as:

[0024]

[0025] Substituting formula (1), the above formula can be written as:

[0026]

[0027] From the above formula, we can see that in θ p direction, the numerator and denominator of the right half of the formula are the same, so they cancel each other out, resulting in θ p Direction signal p (t) is not affected by joint modulation. If the appropriate timing can be designed, p Other signals besides (t) are in θ p The multi-beam timing is considered here. If "1" represents the modulation switch is on and "0" represents the modulation switch is off, then the proposed multi-beam generation timing is optimized after satisfying the following constraints:

[0028]

[0029] The most significant feature of its timing is that at any moment only one unit is in the on-state. Under the modulation of the multi-beam timing represented by the proposed equation (8), the radiation field represented by equation (7) can be written as:

[0030]

[0031] After the time series function is expanded using the Fourier series, its expanded form can be expressed as:

[0032]

[0033] Then the filter filters out the center frequency range [f0-f p / 2,f0+f p / 2], the electromagnetic signal finally radiated by the four-dimensional antenna array can be expressed as:

[0034]

[0035] From the above formula, we can see that the multi-channel signals s1(t),s2(t),…,s Q (t) points to θ1, θ2, …, θ Q In addition, by changing the baseband premodulation signal h pBy optimizing the timing under the constraint of equation (8), the amplitude weighting a can be changed. 0k The value of is used to apply amplitude weighting to each beam to achieve multi-beam forming.

[0036] Next, consider the four-dimensional antenna array for reception, from multiple specified θ1, θ2, ..., θ Q The direction signal received can be expressed as:

[0037]

[0038] After down-converting the signal to baseband, the signal input to baseband can be written as:

[0039]

[0040] Similar to the launch, h is also used p (t) After baseband modulation of the incoming signal, the p-th signal can be expressed as:

[0041]

[0042] The second term of the formula is the interference term caused by the signals received by the receiving beams in other directions. Reasonable optimization of the multi-beam timing parameters (the conduction time of each unit) can suppress or even eliminate it. In this way, R1(t), R2(t), ..., R can be obtained by processing the received baseband signal. Q (t), and then further demodulate to obtain the signals s1(t), s2(t), ..., s received in each specified direction Q (t), realizing the simultaneous reception of multi-beam and multi-path signals.

[0043] In summary, this allows for flexible simultaneous multi-beam scanning during transmission / reception by a four-dimensional antenna array with relatively simple hardware complexity, overcoming the problems of high hardware complexity and low beam control freedom in traditional analog multi-beam forming methods.

[0044] Based on the above principle, the present invention discloses a space-time joint baseband modulation four-dimensional antenna array multi-beam forming system, which includes a modulation timing generator, a baseband signal processor, a mixer, a power splitter / combiner, a time modulation switch, a filter, an amplifier, a circulator, an antenna unit, and optical fibers and cables connecting the various parts; the modulation timing generator is connected to the baseband signal processor and each time modulation switch, the baseband signal processor is connected to the mixer, the mixer is connected to the power splitter / combiner, the power splitter / combiner is connected to the time modulation switch of each channel, each time modulation switch is connected to the filter, and the filter The filter is connected to the amplifier, the amplifier is connected to the circulator, and the circulator is connected to the corresponding antenna units. The modulation timing generator is used to generate the required timing and transmit it to each time modulation switch and the baseband signal processor respectively. The baseband signal processor is used to generate the corresponding pre-modulation processing signal according to the received timing signal to perform baseband modulation on the signal. The amplifier includes a power amplifier for transmission and a low-noise amplifier for reception. The mixer includes an up-converter, a down-converter and a local oscillator signal, which are used to up-convert the transmit signal to radio frequency and down-convert the receive signal to baseband.

[0045] Based on the above principles, the present invention also discloses a space-time joint baseband modulation four-dimensional antenna array multi-beam forming method, which includes the following steps:

[0046] The steps for transmitting with a four-dimensional antenna array are as follows:

[0047] (1) The modulation timing generator generates the modulation timing and divides it into two parts. One part is sent to each modulation switch to perform time modulation on the signal, and the other part is sent to the baseband signal processor. The baseband signal processor generates the corresponding baseband modulation signal according to the timing information to perform baseband modulation on the original signal.

[0048] (2) The baseband signal processor sends the modulated signal to the mixer, which converts the frequency of the signal into a power splitter / combiner. The power splitter / combiner then diverts the RF signal into each modulation switch for time modulation.

[0049] (3) After time modulation, the signal enters the filter, filters out the unwanted sideband signals, retains the center frequency signal, and sends it to the amplifier for amplification;

[0050] (4) After the amplifier amplifies the RF signal, it passes through the circulator and finally transmits it to each antenna unit for multi-beam radiation.

[0051] The steps for receiving with a four-dimensional antenna array are as follows:

[0052] (1) The antenna unit receives the electromagnetic signal in space and sends it to the amplifier for amplification after passing through the circulator;

[0053] (2) The signal amplified by the amplifier is transmitted to the filter, which removes out-of-band noise in the space, and then transmits the signal to the modulation switch for time modulation;

[0054] (3) After the time-modulated signal enters the power splitter / combiner, it is combined by the power splitter / combiner and then transmitted to the mixer for frequency conversion;

[0055] (4) After the mixer converts the signal frequency, the resulting baseband signal is sent to the baseband signal processor, which performs further baseband modulation operations on it and finally decomposes the signals received by multiple beams in space.

[0056] This allows for simultaneous multi-beam generation, allowing for the simultaneous transmission and reception of multiple signals, while maintaining low hardware complexity. Furthermore, by designing the modulation timing and baseband modulation signals, the multi-beams can be shaped to enhance their anti-interference capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of a space-time joint baseband modulation four-dimensional antenna array multi-beam forming system, which includes a modulation timing generator, a baseband signal processor, a mixer, a power splitter / combiner, a time modulation switch, a filter, an amplifier, a circulator, an antenna unit, and optical fibers and cables connecting the various parts; the modulation timing generator is connected to the baseband signal processor and each time modulation switch, the baseband signal processor is connected to the mixer, the mixer is connected to the power splitter / combiner, the power splitter / combiner is connected to the time modulation switch of each channel, each time modulation switch is connected to the filter, and the filter is connected to the amplifier. The amplifier is connected to the circulator, and the circulator is connected to the corresponding antenna unit. Among them, the modulation timing generator is used to generate the required timing and transmit it to each time modulation switch and the baseband signal processor respectively. The baseband signal processor is used to generate the corresponding pre-modulation processing signal according to the received timing signal to perform baseband modulation on the signal. The amplifier includes a power amplifier for transmission and a low-noise amplifier for reception. The mixer includes an up-converter, a down-converter and a local oscillator signal, which are used to up-convert the transmission signal to radio frequency and down-convert the reception signal to baseband.

[0058] Figure 2 A set of multi-beam timing diagrams generated by the proposed method, where the black part indicates conduction and the white part indicates disconnection;

[0059] Figure 3 A set of three-beam patterns generated in the embodiment according to the multi-beam generation step, wherein the three beams are pointed at 15°, 35°, and 50° respectively;

[0060] Figure 4To utilize Figure 3 The demodulation results of the multi-beam transmission of three different OFDM modulated communication signals in the directions of 15°, 35°, and 50° are shown. It can be found that the signals in all directions can be transmitted normally and demodulated normally by the receiver.

[0061] Figure 5 To utilize Figure 3 The signal transmission demodulation results of the multi-beam system simultaneously receiving three different OFDM modulated communication signals at 15°, 35°, and 50° directions show that the signals received in all directions can be correctly received and demodulated.

[0062] Figure 6 This is a timing diagram of low sidelobe multi-beam with a sidelobe level of -25dB. The black part indicates conduction and the white part indicates disconnection.

[0063] Figure 7 A three-beam pattern with a -25 dB sidelobe is generated in the embodiment according to the multi-beam generation step, wherein the three beams are pointed at -30°, 15°, and 40° respectively;

[0064] Figure 8 To utilize Figure 7 The signal transmission demodulation results of three different OFDM modulated communication signals simultaneously transmitted by low sidelobe multi-beam at -30°, 15°, and 40° directions are shown. It can be found that the signals received in all directions can be correctly received and demodulated.

[0065] Figure 9 To utilize Figure 7 The signal transmission demodulation results shown in the figure are that the low sidelobe multi-beam simultaneously receives three different OFDM modulated communication signals in the directions of -30°, 15°, and 40°. It can be found that the signals received in all directions can be correctly received and demodulated. Specific implementation plan

[0066] The embodiment consists of 8 evenly arranged antenna elements, with an element spacing of half a wavelength. Figure 1The structural diagram of the space-time joint baseband modulation four-dimensional antenna array multi-beamforming system is given. The system includes a modulation timing generator, a baseband signal processor, a mixer, a power splitter / combiner, a time modulation switch, a filter, an amplifier, a circulator, an antenna unit, and optical fibers and cables connecting the various parts; the modulation timing generator is connected to the baseband signal processor and each time modulation switch, the baseband signal processor is connected to the mixer, the mixer is connected to the power splitter / combiner, the power splitter / combiner is connected to the time modulation switch of each channel, each time modulation switch is connected to the filter, the filter is connected to the amplifier, the amplifier is connected to the circulator, and the circulator is further connected to each corresponding antenna unit; wherein, the modulation timing generator is used to generate the required timing and transmit it to each time modulation switch and to the baseband signal processor respectively; the baseband signal processor is used to generate a corresponding pre-modulation processing signal based on the received timing signal to perform baseband modulation on the signal; the amplifier includes a power amplifier for transmission and a low-noise amplifier for reception; the mixer includes an up-converter and a down-converter and a local oscillator signal, which are used to up-convert the transmission signal to radio frequency and down-convert the reception signal to baseband.

[0067] When considering the four-dimensional antenna array for transmission, the modulation timing generator is used to generate the modulation timing U k (t) and is divided into two parts, one part is sent to each modulation switch to perform time modulation on the signal, and the other part is sent to the baseband signal processor, which generates the corresponding baseband modulation signal h according to the timing information p (t) for the original signal s p (t) performs baseband modulation; the baseband signal processor sends the modulated signal to the mixer, which converts the frequency of the signal into a power splitter / combiner. The power splitter / combiner diverts the RF signal into each modulation switch for time modulation; after time modulation, the signal enters the filter to filter out unnecessary sideband signals, retain the center frequency signal, and send it to the amplifier for amplification; after the amplifier amplifies the RF signal, it passes through the circulator and finally transmits it to each antenna unit for multi-beam radiation.

[0068] According to the above steps, three radiation beams are generated, and the required timing is as follows: Figure 2 As shown, the modulation frequency is set to 12MHz, and the resulting three-beam pattern is as follows Figure 3 As shown in the figure, the beams are directed to 15°, 35°, and 50° respectively. Using this multi-beam, three different OFDM modulated communication signals (signal bandwidth is 10MHz) are transmitted simultaneously in the directions of 15°, 35°, and 50°. The signal transmission demodulation results are shown in the figure below. Figure 4 It can be found that the signals transmitted using different beams can be effectively demodulated, and the multi-beams generated by the proposed method can effectively transmit multi-path signals.

[0069] Considering the four-dimensional antenna array used for reception, the antenna unit receives the electromagnetic signal in space and sends it to the amplifier for amplification after passing through the circulator; the signal amplified by the amplifier is sent to the filter, which filters out the out-of-band clutter in space, and then sends the signal to the modulation switch for time modulation; the time-modulated signal enters the power splitter / combiner, is combined by the power splitter / combiner, and then sent to the mixer for frequency conversion; after the mixer converts the signal frequency, the resulting baseband signal is sent to the baseband signal processor, which uses the baseband modulation signal h p (t) Further modulation operations are performed on it to finally decompose the signals received by multiple beams in space.

[0070] According to the above receiving steps, three receiving beams are generated. Similarly, the required timing and the generated three-beam directional patterns are also as follows: Figure 2 , Figure 3 As shown. Using this multi-beam to simultaneously receive three different OFDM modulated communication signals in the directions of 15°, 35°, and 50° (signal bandwidth is 10MHz), the signal transmission demodulation results are shown as follows Figure 5 As shown in the figure, it can be found that the different beams generated by the proposed method can receive signals in the corresponding directions and demodulate them successfully.

[0071] On the other hand, by optimizing the timing under the constraint of equation (8), we can apply amplitude weighting to each beam to achieve multi-beam forming. With the sidelobe level of -25dB and the multi-beam pointing to -30°, 15°, and 40° respectively as the target, the optimized timing obtained after optimization is as follows: Figure 6 As shown, in Figure 6 The three-beam pattern under time modulation is as follows Figure 7 As shown. Figure 7 It can be clearly seen that the beam achieves a sidelobe level of -25dB while pointing in the directions of -30°, 15°, and 40°, which can effectively suppress interference in non-target directions. Similarly, according to the above steps of transmitting / receiving signals, the OFDM signal transmission demodulation results when the multi-beam is used for transmission and reception are as follows: Figure 8 , Figure 9 As shown in FIG. 1 , it can be found that the sidelobe suppression multi-beam can also be used to simultaneously receive or transmit signals from multiple directions and demodulate them correctly.

[0072] In summary, the proposed space-time joint baseband modulation four-dimensional antenna array multi-beamforming system and method can simultaneously generate multiple shaped beams with a simple hardware structure. The generated multiple beams can be used to simultaneously transmit multiple signals in different directions or to simultaneously receive multiple signals from different directions.

[0073] While the foregoing descriptions of specific embodiments of the present invention are provided herein, it should be understood that these are presented by way of example only and are not intended to be limiting. Therefore, various modifications in form and detail may be made without departing from the spirit and scope of the present invention, as will be apparent to those skilled in the art and without requiring any inventive step. The foregoing descriptions are to be considered within the scope of the present invention.

Claims

1. A space-time joint baseband modulation four-dimensional antenna array multi-beam forming method, characterized in that: The multi-beam forming system of the four-dimensional antenna array with space-time joint baseband modulation is adopted, which includes a modulation timing generator, a baseband signal processor, a mixer, a power splitter / combiner, a time modulation switch, a filter, an amplifier, a circulator, an antenna unit, and optical fibers and cables connecting the various parts; the modulation timing generator is connected to the baseband signal processor and each time modulation switch, the baseband signal processor is connected to the mixer, the mixer is connected to the power splitter / combiner, the power splitter / combiner is connected to the time modulation switch of each channel, each time modulation switch is connected to the filter, the filter is connected to the amplifier, and the amplifier is connected to the power splitter / combiner. The amplifier is connected to the circulator, and the circulator is connected to the corresponding antenna units; wherein the modulation timing generator is used to generate the required timing and transmit it to each time modulation switch and to the baseband signal processor respectively; the baseband signal processor is used to generate the corresponding pre-modulation processing signal according to the received timing signal to perform baseband modulation on the signal; the amplifier includes a power amplifier for transmission and a low noise amplifier for reception; the mixer includes an up-converter and a down-converter and a local oscillator signal, which are used to up-convert the transmission signal to the radio frequency and down-convert the reception signal to the baseband; when used for transmission, the following steps are included: S1, the modulation timing generator generates the modulation timing and divides it into two parts, one part is sent to each modulation switch to perform time modulation on the signal, and the other part is sent to the baseband signal processor, which generates the corresponding baseband pre-modulation signal according to the timing information to perform baseband modulation on the original signal; S2, the baseband signal processor sends the modulated signal to the mixer, which converts the frequency of the signal into a power splitter / combiner, and the power splitter / combiner divides the RF signal into each modulation switch for time modulation; S3, the signal enters the filter after time modulation, filters out the unnecessary sideband signal, retains the center frequency signal, and sends it to the amplifier for amplification; S4, the amplifier amplifies the RF signal, then passes through the circulator, and finally transmits it to each antenna unit for multi-beam radiation; By changing the baseband premodulation signal h p The angle value θ in (t) p , multi-beam scanning without a phase shifter can be achieved; by optimizing the timing, the value of the amplitude weighting can be changed, and amplitude weighting can be applied to each beam to achieve multi-beam shaping.

2. The space-time joint baseband modulation four-dimensional antenna array multi-beam forming method according to claim 1, further comprising: The baseband premodulated signal h corresponding to the pth beam p (t) is expressed as: Where f0 is the carrier frequency, t is the time, e is the natural base, j is the imaginary unit, E(θ p ,t) is θ p The antenna radiates field in the direction.

3. The space-time joint baseband modulation four-dimensional antenna array multi-beam forming method according to claim 1, further comprising: The timing of the multi-beams is optimized after satisfying the following constraints: Where N is the number of antenna units, U k (t) represents the timing function of the kth unit.

4. A space-time joint baseband modulation four-dimensional antenna array multi-beam forming method, characterized in that: The multi-beam forming system of the four-dimensional antenna array with space-time joint baseband modulation is adopted, which includes a modulation timing generator, a baseband signal processor, a mixer, a power splitter / combiner, a time modulation switch, a filter, an amplifier, a circulator, an antenna unit, and optical fibers and cables connecting the various parts; the modulation timing generator is connected to the baseband signal processor and each time modulation switch, the baseband signal processor is connected to the mixer, the mixer is connected to the power splitter / combiner, the power splitter / combiner is connected to the time modulation switch of each channel, each time modulation switch is connected to the filter, the filter is connected to the amplifier, and the amplifier is connected to the power splitter / combiner. The amplifier is connected to the circulator, and the circulator is connected to the corresponding antenna units; wherein the modulation timing generator is used to generate the required timing and transmit it to each time modulation switch and to the baseband signal processor respectively; the baseband signal processor is used to generate the corresponding pre-modulation processing signal according to the received timing signal to perform baseband modulation on the signal; the amplifier includes a power amplifier for transmission and a low noise amplifier for reception; the mixer includes an up-converter and a down-converter and a local oscillator signal, which are used to up-convert the transmission signal to the radio frequency and down-convert the reception signal to the baseband; when used for reception, it includes the following steps: S1, the antenna unit receives the electromagnetic signal in space and sends it to the amplifier for amplification after passing through the circulator; S2, the signal amplified by the amplifier is transmitted to the filter, the filter filters out the out-of-band clutter in the space, and then the signal is transmitted to the modulation switch for time modulation; S3, after the time modulated signal enters the power splitter / combiner, it is combined by the power splitter / combiner and then transmitted to the mixer for frequency conversion; S4, after the mixer converts the signal frequency, the obtained baseband signal is sent to the baseband signal processor, which performs further baseband modulation operation on it, and finally decomposes the signals received by multiple beams in space; By changing the baseband premodulation signal h p The angle value θ in (t) p , multi-beam scanning without a phase shifter can be achieved; by optimizing the timing, the value of the amplitude weighting can be changed, and amplitude weighting can be applied to each beam to achieve multi-beam shaping.

5. The space-time joint baseband modulation four-dimensional antenna array multi-beam forming method according to claim 4, further comprising: The baseband premodulated signal h corresponding to the pth beam p (t) is expressed as: Where f0 is the carrier frequency, t is the time, e is the natural base, j is the imaginary unit, E(θ p ,t) is θ p The antenna radiates field in the direction.

6. The space-time joint baseband modulation four-dimensional antenna array multi-beam forming method according to claim 4, further characterized by The timing of the multi-beams is optimized after satisfying the following constraints: Where N is the number of antenna units, U k (t) represents the timing function of the kth unit.

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